Sediments and the Reef!!

Does sediment have any impacts on the Great Barrier Reef??

Let's first look at the history of the reef.

The Great Barrier Reef is one of the seven wonders of the natural world. It was declared a World Heritage area in 1981 and added to the Natural Heritage List in 2007.

Stretching 2300 kilometres, this natural icon is so large it can even be seen from outer space.  It covers an area about 344,400 km^{2 .}

It includes some 3000 coral reefs, 600 continental islands, 300 coral cays and about 150 inshore mangrove islands.

It  extends south from the northern tip of Queensland in north-eastern Australia to just north of Bundaberg.

The Reef is about 500,000 years old, in it's present form it is estimated to be between 6000 to 8000 years old. 

Sediments have been running into the waters of the Great Barrier Reef since it was first formed.  The massive river systems in northern Queensland have been dumping millions and millions of tonnes of sediment for thousands of years with no effect to the reef!

So, how can the suspended sediments from dredging at Abbot Point cause any harm to the reef, when sediments from rivers systems have been doing the exact same for thousands of years??

The reef has known stresses as stated by the Australian Institute of Marine Science.  Coral bleaching, storm damage and Crown of Thorns Starfish.  Now, we know you cannot stop mother nature as in the form of storms damage, but, coral bleaching and Crown of Thorns Starfish.  What has caused these to take over the reef??  Could it be from pollutants coming out of the river systems from farming practices?? A new report from the AIMS states that this could be the case!!

Courier Mail Article

In the above article it is stated: -  MILLIONS of tonnes of farm-based and naturally occurring pollutants are flooding the Great Barrier Reef each year, choking sea grasses, starving marine life and killing coral.  The report said the state’s rivers discharge 17 million tonnes of suspended sediments, 80,000 tonnes of nitrogen, and 16,000 tonnes of phosphorus annually to the reef, up to eight times the level compared with pre-European times, strongly suggesting farming and development were responsible. It found flooding also had a dramatic impact on water quality and the discharge from rivers determined water clarity on the reef.

 So, pollutants in my opinion are what have caused the stress to the reef , not sediment itself , but , what is in the sediment!!

The seabed floor at Abbot Point has been tested and found to be non toxic, so , therefore , the sediments stirred up from the dredging should have no effect on the local eco systems!!

Here is another link to a good article about reefs surviving in a sediment rich environment. More proof that sediments itself is not the main problem for the reef!!

Coral Reef Thriving in sediment laden waters.

Quoted from the above article:-

Rapid rates of coral reef growth have been identified in sediment-laden marine environments, conditions previously believed to be detrimental to reef growth. A new study has established that Middle Reef – part of Australia’s iconic Great Barrier Reef – has grown more rapidly than many other reefs in areas with lower levels of sediment stress. This image shows Middle Reef from above the water.

Abbot Point dredging details -

North Queensland Bulk Ports Corporation (NQBP) has a long and respected history of successfully delivering dredging projects at its various ports. For over three decades NQBP has been undertaking dredging programs to ensure the safe navigation of ships and port efficiency.

As the port authority for some of Australia’s largest ports, NQBP follows an approach based on sustainable planning, thorough environmental management and rigorous environmental monitoring.
A dredging campaign is required at Abbot Point to achieve the required depths in the berth pockets and departure area for new coal terminal expansions at the port: T0, T2 and T3.


Key Facts About the Proposed Dredging Campaign

The Approval Process
The project is being assessed under the Commonwealth’s Environmental Protection and Biodiversity Conservation Act 1999.
It has been deemed a controlled action under the Act and is assessable by Public Environment Report (PER). Comments are currently being sought from the public on the PER. Comments close on 15 February.


The Location
The dredged material will be removed from future berth and apron areas within the specified Abbot Point port area, adjacent to the existing offshore berths.
The area to be dredged covers about 180 hectares.


Volume of Dredged Material
Up to three million cubic metres of clean material will be dredged.


Dredging Timing
It is estimated the dredging will take a total of about 10 weeks, over a number of campaigns. Dredging and disposal will only be carried out between April and October to avoid the turtle nesting and wet seasons.


Why Offshore Disposal?

Dredged material disposal at sea requires extensive analysis of alternatives in accordance with international protocols (London Convention) and Commonwealth requirements (Environment Protection (Sea Dumping) Act 1981)).

Decisions with regards to dredging are based on the best overall environmental outcome.

Offshore disposal was chosen to achieve the best environmental outcomes. This decision was arrived at after a comprehensive workshop was undertaken along with the regulators. Sea disposal was determined a superior option compared to land disposal and the significant environmental and cultural heritage issues that would result.

Disposal Location and Plume Footprint

The dredged material will be disposed at a designated location about 25 kilometres offshore, away from coral reefs, in about 40 metres of water depth. The seabed at the disposal area does not contain any habitat of ecological significance.

Release of the dredged material will occur under the water surface and most of the coarse material will fall out of the water column and settle primarily within the disposal area boundary. Some fine sediment in the dredged material will be suspended in the water column and travel in a north westerly direction (away from Holbourne Island).

Impact on Holbourne Island
Expert and peer reviewed 3D modelling of the distribution of the dredged material plume indicates that the plume will not reach Holbourne Island.


No Toxic Materials

Sediment analysis was carried out following the National Assessment Guidelines for Dredging and identified no contaminants present in the sediment at levels that could result in environmental harm.

Only material that has been tested and determined suitable for ocean disposal, and not toxic or hazardous material, can be disposed of at sea.

Ongoing Water Quality Monitoring

A water quality monitoring program has already been implemented and incorporates the latest scientific thinking with key criteria based on the protection of ecological communities present at Abbot Point.

This is a long-term program which will continue after dredging occurs.

Marine Environment Impacts

Marine ecology surveys of the disposal site and the surrounding area did not identify any communities or habitat with unique or high ecological values. While some impacts may occur, they will be minor and short-term.

Fishing Impacts

The scientific studies and modelling carried out show any impacts from dredging will be temporary and will not impact fishing in the long-term.

Plume modelling shows suspended sediment will not affect habitat such as coral reefs that may support finfish species.

However, NQBP will work with the fishing community and scientific experts to ensure that any impacts to fisheries are monitored throughout the project and will look at options for establishing a long-term management strategy.

Impact on the Caley Valley Wetlands
There will be no impact on the Caley Valley Wetlands from this dredging project.